Activity-related changes in intracellular pH in rat thalamic relay neurons

Activity-related shifts in intracellular pH (pH(i)) can exert potent neurom odulatory actions. Different states of neuronal activity of thalamocortical neurons were found to differentially modulate pHi. Tonic activity evoked b y injection of depolarizing current led to a reversible rise in [H+](i) whi ch was nearly abolished in the presence of TTX. Block of voltage-gated calc ium channels with 1 mM Ni2+ reduced the [H+](i) transients related to tonic activity. Rhythmic activation of burst discharges caused changes of [H+](i ) which were decreased by TTX, whereas 1 mM Ni2+ almost abolished the [H+]( i) transients. the present results show that different forms of neuronal ac tivity can lead to intracellular acidification caused by different mechanis ms, i.e. Na+ and Ca2+ influx through sodium and Ca2+ channels, respectively , and the subsequent activation of a Ca2+/H+ pump; The resulting acidosis i s suggested to reduce further Ca2+ influx and prevent excessive neuronal ex citation. NeuroReport 11:33--37 (C) 2000 Lippincott Williams & Wilkins.